Now registered Windows Phone developers can receive pre-release OS updates on their dev phone, directly from Microsoft! You can use this app to opt-in your phone to receive early Windows Phone updates before they are generally available, enabling you to run and test your app on real hardware running the latest OS before your customers.
IMPORTANT REQUIREMENTS AND NOTES:
• You must meet one of the following three requirements: (a) have an active Windows Phone Dev Center account; (b) have an active App Studio account; OR (c) be running a registered developer device (‘dev unlocked’ phone)
• Updates will only include the Microsoft update, and not additional OEM drivers/firmware
• To ensure the best experience, your device must be running the latest OS release (currently 8.0.10322.71) or greater to receive early updates via this program
• You will be required to accept additional terms & conditions within the app prior to opt-in
• You CANNOT REVERT to a prior OS version once you have taken an update via this program
Key features:
• Access to latest pre-release Windows Phone updates
• Ability to opt-out of pre-releases and only receive production Windows Phone updates
http://windowsphone.com/s?appId=178ac8a1-6519-4a0b-960c-038393741e96
How to get Developer account
or
IMPORTANT REQUIREMENTS AND NOTES:
• You must meet one of the following three requirements: (a) have an active Windows Phone Dev Center account; (b) have an active App Studio account; OR (c) be running a registered developer device (‘dev unlocked’ phone)
• Updates will only include the Microsoft update, and not additional OEM drivers/firmware
• To ensure the best experience, your device must be running the latest OS release (currently 8.0.10322.71) or greater to receive early updates via this program
• You will be required to accept additional terms & conditions within the app prior to opt-in
• You CANNOT REVERT to a prior OS version once you have taken an update via this program
Key features:
• Access to latest pre-release Windows Phone updates
• Ability to opt-out of pre-releases and only receive production Windows Phone updates
http://windowsphone.com/s?appId=178ac8a1-6519-4a0b-960c-038393741e96
How to get Developer account
or
You can either pay $19 for a developer license or you can get the update free if you are using the Windows Phone App Studio
You will also need to developer unlock your phone which allows installation of pre-release updates on your device
More information on how to do that can be fount here
https://dev.windowsphone.com/en-us/join
terms and conditions can also be found here
http://dev.windowsphone.com/en-us/featured/update3#Terms